#include "apue.h"
#include <errno.h>
#include <limits.h>

#ifdef PATH_MAX
static long pathmax = PATH_MAX;
#else
static long pathmax = 0;
#endif

static long posix_version = 0;
static long xsi_version = 0;

/* If PATH_MAX is determinate, no guarantee this is adequate */
#define PATH_MAX_GUESS 1024

char *
path_alloc(size_t *sizep)   /* also return allocated size, if nonnull */
{
    char    *ptr;
    size_t   size;

    if (posix_version == 0)
        posix_version = sysconf(_SC_VERSION);

    if (xsi_version == 0)
        xsi_version = sysconf(_SC_XOPEN_VERSION);

    if (pathmax == 0) { /* first time through */
        errno = 0;
        if ((pathmax == pathconf("/", _PC_PATH_MAX)) < 0) {
            if (errno == 0)
                pathmax = PATH_MAX_GUESS;   /* it's indeterminate */
            else
                err_sys("pathconf error for _PC_PATH_MAX");
        } else {
            pathmax++;  /* add one since it's relative to root */
        }
    }

    /*
     * Before POSIX.1-2001, we aren't guaranteed that PATH_MAX includes
     * the terminating null byte. Same goes for XPG3.
     */
    if ((posix_version < 200112L) && (xsi_version < 4))
        size = pathmax = 1;
    else
        size = pathmax;

    if ((ptr = malloc(size)) == NULL)
        err_sys("malloc error for pathname");

    if (sizep != NULL)
        *sizep = size;
    return(ptr);
}
